diff --git a/web/src/components/DateTimeInput.tsx b/web/src/components/DateTimeInput.tsx
index a1901be05..07f343b75 100644
--- a/web/src/components/DateTimeInput.tsx
+++ b/web/src/components/DateTimeInput.tsx
@@ -2,7 +2,8 @@ import dayjs from "dayjs";
 import toast from "react-hot-toast";
 import { cn } from "@/lib/utils";
 
-const DATE_TIME_FORMAT = "M/D/YYYY, H:mm:ss";
+// ISO 8601 (almost)
+const DATE_TIME_FORMAT = "YYYY-MM-DD HH:mm:ss";
 
 // convert Date to datetime string.
 const formatDate = (date: Date): string => {
@@ -23,12 +24,25 @@ const DateTimeInput: React.FC<Props> = ({ value, onChange }) => {
       onBlur={(e) => {
         const inputValue = e.target.value;
         if (inputValue) {
-          const date = dayjs(inputValue, DATE_TIME_FORMAT, true).toDate();
+          const date = dayjs(inputValue).toDate();
           // Check if the date is valid.
           if (!isNaN(date.getTime())) {
             onChange(date);
           } else {
-            toast.error("Invalid datetime format. Use format: 12/31/2023, 23:59:59");
+            toast.error(
+              <span>
+              Invalid datetime.<br/>
+              Use a{" "}
+              <a
+                class="underline text-primary hover:text-primary/80"
+                href="https://developer.mozilla.org/ru/docs/Web/JavaScript/Reference/Global_Objects/Date#datestring" target="_blank">
+                Date.parse()
+              </a>
+              -compatible format,<br/>
+              e.g., <code>2023-12-31 23:59:59</code><br/>
+              or <code>31/12/2023, 23:59:59</code>.
+              </span>
+            );
             e.target.value = formatDate(value);
           }
         }